1. Field of the Invention
The present invention relates to a radio-frequency (RF) processing circuit and a wireless communication device, and more particularly, to an RF processing circuit and a wireless communication device for supporting multiple-input multiple-output (MIMO) technique and adjusting transmissions of signals according to channel conditions.
2. Description of the Prior Art
With the advancement of wireless communication, different wireless communication systems have been developed, such as mobile communication system, wireless local area network (WLAN) and wireless personal area network (WPAN). For example, the mobile communication system can be Global System for Mobile Communications (GSM), 3rd generation (3G) or long term evolution (LTE), the WLAN can be Wi-Fi or Worldwide Interoperability for Microwave Access (WiMAX), and the WPAN can be Bluetooth. Preferably, different wireless communication systems operate on different operation frequency bands and use different communication technologies (e.g. modulation, coding and/or ciphering), to avoid mutual interference between wireless signals of different wireless communication systems. However, some of the wireless communication systems must operate on the same operation frequency band due to limited spectrum resources.
For example, operation frequency bands of Bluetooth (e.g. IEEE 802.15.1) and Wi-Fi (e.g. IEEE 802.11) are on the industrial, scientific medical (ISM) band located around a carrier frequency of 2.4 GHz, and the ISM band is reserved internationally for industrial, scientific and medical applications. Therefore, there may be a wireless communication device using Bluetooth and Wi-Fi on the same operation frequency band at the same time. In this situation, when a wireless signal of Bluetooth or Wi-Fi is transmitted and received via an antenna, a wireless signal of the other must stop transmitting and receiving via the same antenna even though different protocols with different modulations and codings are respectively used for Bluetooth and Wi-Fi. In other words, transmission or reception of the wireless signal of Bluetooth or Wi-Fi occupies the antenna.
On the other hand, multi-input multi-output (MIMO) technique has been used to increases a data rate of wireless signals. That is, multiple antennas are used in a transceiver to transmit/receive a wireless signal for providing a signal processing gain, to improve quality of a corresponding received wireless signal. Therefore, the received wireless signal is highly possible to be recovered correctly, and the data rate of the wireless signals can be increased. However, when a wireless communication device is equipped with multiple antennas (e.g. two antennas), and must process the wireless signals of Bluetooth and Wi-Fi at the same time, the two antennas are respectively used for processing the wireless signals of Bluetooth and Wi-Fi. In other words, each of Bluetooth and Wi-Fi can only occupies one of the two antennas, and cannot utilize MIMO technique. Therefore, when a wireless communication device must process the wireless signals of Bluetooth and Wi-Fi at the same time, MIMO technique can not be enabled to increase the data rate of the wireless signals.
The above situations are frequently happened to a computer system including a wireless communication device with MIMO technique. For example, a user uses the computer system to surf the Internet via Wi-Fi, and uses a headphone, a keyboard or a mouse via Bluetooth at the same time. Please note that, the above situations are illustrated by using Bluetooth and Wi-Fi which are frequently installed in a same electronic device, such as a notebook, a mobile phone, etc. The user is highly possible to use Bluetooth and Wi-Fi at the same time such that MIMO technique cannot be enabled and the data rate of the wireless signals can not be increased. However, the same problem also exists to other wireless communication systems operating on the same operation frequency band.
Besides, according to contents included in wireless signals or a user input, the priorities of the wireless signals are typically different. For example, transmissions of voice or data in a wireless communication system can only begin after a control message is correctly received and recovered. Therefore, a priority of a wireless signal including the control message is usually higher than that of other wireless signals. Further, an amount of resources for correctly receiving and recovering the control message is usually large due to the instability of a wireless channel, wherein most part of the resources are wasted for retransmitting the control message.
Therefore, how to utilize MIMO technique for increasing the data rate of the wireless signals, and increasing a probability of correctly recovering the wireless signal with the higher priority are topics to be discussed and addressed.